Jamestown Canyon Virus: What to Know

Medically Reviewed by Neha Pathak, MD on August 23, 2022

Mosquitoes can be pesky critters, buzzing about and triggering itchy welts when they bite. Most are harmless, but some carry and spread deadly diseases like Jamestown Canyon virus.

Many people infected are asymptomatic or have no symptoms. But those who do report fever, fatigue, headache, or more serious problems. Death is rare.

There’s no way to treat or prevent Jamestown Canyon virus. But here’s a closer look at what it is and how you can avoid it.

How Do Mosquitoes Spread Jamestown Canyon Virus?

The virus was discovered in 1961 in mosquitoes from Jamestown Canyon, Colorado. Now, it’s pretty much all over the U.S. and North America, but cases are more common in upper Midwest states. You can also catch the disease at any time, but you’re more likely to get it between late spring and mid-fall.

Mosquitoes can become infected when they feed on deer and other animals that have the virus in their blood. But Jamestown Canyon virus is not contagious. It only spreads through mosquito bites. This means that you can’t get it if someone who’s infected touches you or coughs and sneezes around you.

What Are the Symptoms of Jamestown Canyon Virus?

Many people infected don’t have symptoms. But if you do, flu-like symptoms can start anywhere from a few days after an infected mosquito bites you to 14 days.

Early symptoms may include:

  • Fever
  • Fatigue
  • Headache
  • Cough
  • Sore throat
  • Runny nose

In serious cases, the virus can lead to meningitis (when the membranes covering your brain and spinal cord are inflamed) and encephalitis (inflammation of the brain).

Watch out for symptoms like:

  • Stiff neck
  • Confusion
  • Loss of coordination
  • Difficulty speaking
  • Seizures

Get emergency help right away if you have any of these.

How Is Jamestown Canyon Virus Diagnosed?

Call your doctor if you think you might be infected. They’ll ask you about any recent travels and order blood tests to check for the virus.

How Is Jamestown Canyon Virus Disease Treated?

There’s no medication available to treat Jamestown Canyon virus disease. There are no vaccines to prevent it, either.

If you’ve been infected with the virus, you should:

  • Get plenty of rest
  • Drink fluids to prevent dehydration
  • Take over-the-counter pain medication to ease fever and headache

How Do You Prevent Mosquito Bites?

Since Jamestown Canyon virus spreads through infected mosquitos, the best way to prevent or lower your risk for an infection is to avoid getting bitten by one in the first place.

You should:

Use insect repellent. Try one that’s approved by the Environmental Protection Agency (EPA). If you use it as directed, it’s safe and effective if you’re pregnant or breastfeeding. When you’re choosing a repellent, look for active ingredients, such as:

  • DEET
  • Picaridin (Also known as KBR 3023). It might be called icaridin outside the U.S.
  • IR3535
  • Oil of lemon eucalyptus (OLE)
  • Para-menthane-diol (PMD)
  • 2-undecanone

When you’re using it on children, don’t spray or apply it on or near their hands, eyes, mouth, cuts, or irritated skin. Spray it on your hands first then apply it on your child’s face. It’s best to use the repellent on top of sunscreen.

Wear long-sleeved shirts and pants. Your odds of getting bitten are higher when you’re outdoors. Cover as much skin as possible. If you’re planning to go to a mosquito-infested area, wear permethrin-treated clothing and gear. It’s a type of insecticide that kills or repels mosquitoes. But don’t use permethrin products directly on your skin. It might irritate you.

Stop mosquitoes from getting inside your home. Use screens on your doors and windows to keep mosquitoes out of your home. They can sneak through the smallest opening, so make sure to mend any holes or tears in your screens. Use air conditioning when possible.

Control mosquitoes outdoors. Mosquitoes lay eggs in or near standing water. Make sure to empty, turn over, get rid of, or clean items like mugs, buckets, pools, birdbaths, flowerpots, tires, gutters, or any container that might hold water for a long time. Also, clean and chlorinate your swimming pools when you’re not using them.

This will stop the mosquito population from growing in and around your home and neighborhood.

Avoid mosquito bites during travel. If you’re planning to travel to mosquito-infested areas, especially during the breeding season, you should:

  • Pick a hotel with screens and AC if possible.
  • Use a mosquito net, especially if you’re camping or sleeping outside.
  • Avoid sleeping directly next to the mosquito net as they can still bite you through the small holes.
  • Use plug-in repellents.

Show Sources


CDC: “Jamestown Canyon Virus,” “Control Mosquitoes Inside Your Home.”

Minnesota Department of Health: “Jamestown Canyon Virus Fact Sheet.”

Oakland County Michigan: “Jamestown Canyon Virus.”

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